Use, like scrumpy? (5)
I believe the answer is:
apply
'use like scrumpy?' is the definition.
'apply' can be an answer for 'use' ('apply' can be a synonym of 'use'). I'm unsure of the 'like scrumpy?' bit.
'use like' is the wordplay.
'use' becomes 'app' (I can't explain this - if you can you should believe this answer much more).
'like' becomes 'ly' ('ly' can be similar in meaning to 'like').
'app'+'ly'='APPLY'
(Other definitions for apply that I've seen before include "Employ; be relevant" , "Make use of" , "Be relevant - seek job" , "Put to use" , "concentrate" .)